Implementing fuse by using small trace width

[avib]

Hi,
I'm implementing a board that will have two external lines.this two lines will be connected to a mosfet which will behave as a switch to connect between them.
the maximum current that I allow on the lines is 1A. I want to put a protection on the traces by using a fuse, but I don't want to use a "real" fuse. I plan to put two pads of resistor (1206 size) in serial with one of the lines and connect between them a line with a small trace width. my question is how can I calculate the trace width of the "fuse" that will be disconnected by overcurrent?
Note that each of the lines has a trace width of 40 mil which was calculated by a web calculator in the following site:

http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm

Thanks,
Avi

 

[edfair]

Your fuse will have problems. There is no board manufacturing process that can control trace sizes in the dimensions you are going to need.

Buy a fuse AGC1 and break it and mike the element. That will give you the diameter from which you can calculate the area. Using trace thickness as one dimension I think you will find you'll need a trace of less than .001.

Better to think PICA fuse. Ed Fair
unixstuff@juno.com
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